U.S. patent number 5,330,721 [Application Number 08/045,534] was granted by the patent office on 1994-07-19 for step pipette.
This patent grant is currently assigned to Nippon Zeon Company, Ltd.. Invention is credited to Jukka Tervamaki.
United States Patent |
5,330,721 |
Tervamaki |
July 19, 1994 |
**Please see images for:
( Certificate of Correction ) ** |
Step pipette
Abstract
A step pipette, which has a dosing rack and therein a dosing
toothing, a strike meshing with the dosing toothing, a filling rack
connected with the dosing rack by a gear, a striker spring as well
as a release member for releasing the tension of the striker spring
after the last full-lenght stroke. The solution ensures that also
the last liquid dose is always full.
Inventors: |
Tervamaki; Jukka (Helsinki,
FI) |
Assignee: |
Nippon Zeon Company, Ltd.
(Tokyo, JP)
|
Family
ID: |
8535106 |
Appl.
No.: |
08/045,534 |
Filed: |
April 9, 1993 |
Foreign Application Priority Data
Current U.S.
Class: |
422/515; 422/928;
436/180; 73/864.13 |
Current CPC
Class: |
B01L
3/0234 (20130101); Y10T 436/2575 (20150115) |
Current International
Class: |
B01L
3/02 (20060101); B01L 003/02 () |
Field of
Search: |
;422/99,100 ;436/180
;73/864.11,864.13,864.16 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
|
|
|
|
|
|
|
58875 |
|
Nov 1981 |
|
FI |
|
WO84/04056 |
|
Oct 1984 |
|
WO |
|
2045641 |
|
Jun 1983 |
|
GB |
|
Primary Examiner: Housel; James C.
Assistant Examiner: Tran; Lien
Attorney, Agent or Firm: Armstrong, Westerman, Hattori,
McLeland & Naughton
Claims
I claim:
1. A step pipette, comprising:
a frame;
a cylinder provided on said frame;
a piston provided within said cylinder and movable in a direction
between a lower and an upper position within said cylinder;
a dosing rack supported by said frame which is parallel to said
direction and which is fixed to said piston, said dosing rack being
provided with a dosing toothing;
a striker supported by the frame and movable between an upper and a
lower position, a portion of said striker capable of meshing with
the dosing toothing for transferring the dosing rack and the piston
downwards by predetermined strokes;
said dosing rack also including a longitudinal transmission
toothing, a gear in mesh with said longitudinal transmission
toothing and supported by said frame, a filling rack supported by
said frame parallel with the dosing rack, a second longitudinal
transmission toothing provided on said filling rack, which is in
mesh with the gear from the opposite side relative to the
transmission toothing of the dosing rack;
a striker spring means for pressing the striker against the dosing
toothing;
a release element means on the filling rack for releasing the
tension of the striker spring after a last full-length stroke
thereby disengaging said striker form said dosing toothing;
a loosening spring for moving the striker from the dosing toothing
to an upper disengaged position after the last full-length stroke
to thereby allow filling of the cylinder by retraction of the
piston;
means for reengaging said striker with the dosing rack.
2. A pipette according to claim 1, wherein the loosening spring
simultaneously acts as a return spring for the striker for
returning it into the upper position after a stroke of the
striker.
3. A pipette according to claim 1, wherein the force of the
loosening spring is lower than a force maintaining the striker
during a stroke in the dosing toothing without the striker spring
means.
4. A pipette according to claim 1, wherein the release element
means is a release member moving together with the filling
rack.
5. A pipette according to claim 4, wherein the striker spring means
has a free end bearing against the filling rack and the release
member is a deviation located in the filling rack, into which
deviation the free end of the striker spring means is positioned
after the last full-length stroke such that the tension of the
striker spring is released.
6. A pipette according to claim 5, wherein the striker is
journalled at a journalling point on a lever which is movable
between a lower and an upper position and the striker spring means
is a striker spring having an upside-down V shape.
7. A pipette according to claim 6, wherein the loosening spring is
fixed to the striker proximate the journalling point at a location
so as to draw the striker upwards away from said cylinder.
8. A pipette according to claim 1, further including an adjusting
rod located on a side of the dosing toothing and movable along the
dosing toothing, at the lower end of the adjusting rod there is a
cam, which loosens the striker from the dosing toothing when the
striker is moved upwards away from said cylinder.
Description
FIELD OF INVENTION
The invention relates to step pipettes, by means of which liquid
drawn by a piston may be dosed out in several smaller doses.
BACKGROUND OF ART
Step pipettes are known, which have a piston movable in a cylinder,
a longitudinal pinion rack in a piston rod, a striker bearing
against the pinion rack by the force of a spring as well as
actuator for the striker, by means of which actuator the striker is
forced to push the pinion rack drawn upwards and thereby also the
piston by a desired distance downwards shorter than the entire
moving distance of the piston. In the publications FI-60137
(corresponds to GB-2045641) and FI-77166 (corresponds to WO
84/04056), such pipettes are described, which additionally have a
filling rack connected to the piston rod by means of a pinion,
which filling rack is pressed to draw the piston to its upper
position.
One problem in connection with e.g the above-mentioned step
pipettes has been the fact that the last dose to be injected out
often remains incomplete, since the pinion rack is no longer
capable of transferring by the entire desired distance.
GENERAL DESCRIPTION OF INVENTION
The main object of the invention is to provide a step pipette
furnished with a press-down filling rack, in which step pipette
also the last liquid dose injected out is full. This is achieved by
means described in claim 1. Certain preferred embodiments are
described in the other claims.
Essential in the invention are a striker bearing against a pinion
rack by a force of a spring as well as a release mechanism for the
spring of the striker, which release mechanism prevents the striker
from engaging the pinion rack, when there is no longer a full dose
to be pressed out.
BRIEF DESCRIPTION OF THE DRAWINGS
FIGS. 1-3 show the pipette in various steps of operation.
DETAILED DESCRIPTION OF EMBODIMENT OF INVENTION
A preferred embodiment of the invention is next described in more
detail.
The main parts (FIG. 1) of the pipette are a hollow, longitudinal
handle 1 and a cylindrical piece 2 located at its lower end. To the
cylindrical piece is fitted a piston 3 movable in a cylinder 4. The
jet of the cylindrical piece is tapered and a jet container for
liquid is intended to be fixed thereto.
To the upper end of the rod of the piston 3 has been fixed a dosing
rack 5. It has been fitted to be slidable in the longitudinal
direction of the handle on its one side. The rack 5 has been fixed
to the rod of the piston 3 by means of an extension 6 extending to
the middle of the handle.
At the upper end of the dosing rack 5, on its inwardly extending
side, has been located a dosing toothing 7. Together therewith
operates a striker 8, which has been journalled on a lever 9 at a
point 10. The free end of the lever 9 extends from an opening in
the handle outside the handle into the side of its dosing tube 5.
On the opposite side, the other end of the lever 9 has been
journalled on the handle at a point 11.
There is a sharp pick point at the lower end of the striker 8,
which point engages the dosing toothing 7, when the lever 9 is
pressed downwards.
The striker 8 has been also connected with a striker spring 12,
which presses the striker against the dosing toothing 7.
When the dosing rack 5 rises up, the piston 3 sucks in liquid. By
means of the lever 9 and the striker 8, it is possible to push the
rack 5 and thereby also the piston 3 downwards by predetermined
steps and thereby also to dose the liquid sucked in as smaller,
predetermined doses (FIG. 2).
The dosing rack 5 is drawn up by means of a filling rack 13 (FIG.
1). It is parallel to the dosing rack 5 and placed on the handle on
the opposite side relative to the dosing rack. At the lower end of
each rack 5 and 13 have been located on sides opposite to each
other longitudinal equally divided toothings 14 and 15 as well as a
gear 16 located therebetween and in mesh with both of them. The
upper end of the filling rack 13 extends outside the handle. When
the filling rack 13 is thus pressed into the lower position, the
dosing rack 5 rises up into its upper position. Similarly, when the
dosing rack 5 is pressed downwards, the filling rack 13 transfers
upwards.
One end of the striker spring 12 (in this connection a V-shaped
wire or leaf spring fitted around the journalling point 10) has
been fixed to the striker 8 and the other, free end 17 bears
against the filling tube 13 such that the spring tends to press the
striker towards the dosing toothing 7. As a release element of the
striker spring 12 is in this case a gap, a slot, a hole or a rack
end 18 located approximately in the middle of the filling rack 13,
which rack end acts as a deviation for the free end 17 of the
spring. When the free end 17 contacts the deviation 18, the tension
of the spring 12 is released.
The location of the deviation 18 in the filling rack 13 is
determined such that the end 17 of the spring 12 contacts the
deviation during the last full dosing stroke. However, owing to the
friction between the dosing toothing 7 and the point of the striker
8. The striker does not disengage from the toothing 7 during the
stroke, until after it returns to the upper position (FIG. 3).
The striker 8 is also in connection with a loosening spring 19 for
loosening the striker from the toothing 7. The loosening spring 19
is a draw-spring, whose upper end has been fixed to the handle
above the striker 8 at a point 20 and whose lower end has been
fixed to the striker 8 eccentrically relative to the journalling
point 10 to a point 21 such that the return spring also tends to
turn the striker out of the toothing 7. At the same time, the
return spring 18 acts as a return spring for the lever 9.
Naturally, the force of the loosening spring 19 must not be so high
that the striker would loosen from the toothing 7 during the last
stroke, when the end 17 of the spring 12 enters into the deviation
18. The friction force between the striker 8 and the toothing 7 is
first of all determined by the friction between the piston 3 and
the cylinder 4. When so desired, the loosening during the stroke
may also be prevented by means of a suitable design of the point of
the striker 8 and the toothing 7.
The lower limit of the movement of the striker 8 is determined by a
limiter 22 fixed to the handle (FIG. 2). The striker 8 extends in
the cross direction to the side of the dosing toothing 7. The
engagement point of the striker 8 with the toothing 7 is determined
by an adjusting rod 23 parallel with the toothing 7 and placed on
its side. Its lower end has been rounded into a cam 24, which rises
the striker 8 out of the toothing 7 during the rising-up step of
the striker. When the striker 8 is pressed down, its point is
pressed into the toothing 7 immediately from below the cam 24.
For adjusting the lenght of the dosing stroke, the adjusting rod 23
has been made movable in the longitudinal direction relative to the
handle. Therefore, on the upper end of the rod 23 has been
journalled an adjusting wheel 25, whose axis extends across a
longitudinal groove of the rod. In addition, the rod 23 has been
eccentrically journalled on the wheel 25. When the wheel is thus
turned, the rod 23 may be transferred (FIG. 1).
The FIGURES show only a one-channel pipette, but the invention may
naturally, as such, be applied also to multiple-channel
pipettes.
* * * * *